The present invention generally relates to electronic thermometers. More specifically, the present invention relates to an electronic thermometer having a contact sensor that allows the thermometer to more rapidly obtain accurate temperature measurements from a patient.
It is common practice in the medical field to determine the body temperature of a patient by means of a temperature sensitive device that not only measures the temperature of the patient but also displays that temperature to the caregiver. Such temperature measurements are taken routinely in hospitals and in doctors' offices. Presently available electronic thermometers can take tens of seconds in its predictive mode and five or more minutes in its monitoring or direct reading mode to return a temperature to the caregiver. Electronic predictive thermometers have become popular because in their predictive mode, the time for taking the temperature is much less than a mercury thermometer. For busy nursing staff, time is of the essence and any reduction in the amount of time to obtain a temperature measurement allows the nursing staff to be more productive.
An inherent characteristic of electronic thermometers is that they do not instantaneously measure the temperature of the sites to which they are applied. It may take a substantial period of time before the temperature sensitive device stabilizes at the temperature of the site such that the temperature indicated by the thermometer is representative of the actual temperature of the body or sight being measured. This lag is caused by the various components of the measurement system that impede heat flow from the surface of the body or site to the temperature sensor.
One common approach to shortening the amount of time required for an electronic thermometer to take an accurate reading of a patient's temperature is to preheat the probe tip of the thermometer to a temperature close to the expected patient temperature. Such probe tip heaters have been known for many years and are shown in U.S. Pat. Nos. 5,632,555; 6,495,806 and 6,698,921 as an example. A commercially available product that utilizes a probe tip heater is the Turbo-Temp™ electronic thermometer available from IVAC®.
In prior art electronic thermometers that utilize a probe tip heater to raise the tip temperature prior to insertion of the probe into the patient's mouth, the control unit of the thermometer heats the probe tip to a temperature well below the normal human core body temperature of 98.6° F. In the presently available electronic thermometers, the processing circuitry within the electronic thermometer monitors for a rise in the temperature at the probe tip as an indicator that the probe tip has been properly positioned either within the patient's mouth or at another acceptable location.
Since the electronic circuitry monitors for an increase in the temperature at the probe tip to indicate contact with the patient, the temperature of the probe tip must be kept well below the normal human body temperature of 98.6° F. As an example, current electronic thermometers that utilize probe tip heating maintain the probe tip at a temperature of approximately 93° F. Thus, when the probe tip is placed within the patient's mouth, the temperature of the probe tip must elevate to approach the temperature of the patient. This rise in temperature creates a delay in measuring the patient's temperature. As can be readily understood, electronic thermometers that maintain the probe tip temperature at approximately 93° F. cannot be used in the predictive mode when the ambient temperature is above 93° F. since the temperature of the probe tip will be at the ambient temperature. Since the electronic circuitry monitors for an increase in temperature at the probe tip, the change in the temperature will be difficult to detect when the probe tip is at an ambient temperature above 93° F.
Therefore, it would be desirable to increase the speed at which the patient's temperature may be taken by increasing the temperature of the probe tip prior to determining the patient's temperature. Further, it would be desirable to provide a system that would enable the use of the predictive mode of the electronic thermometer at higher ambient temperatures.